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My Monterey

Anti-Siphon Valve

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I'm working through some fuel starvation issues on the port side engine of my boat. It's a 5.7GXI-E. One of the things it could be is the anti-siphon valve. I can do the pressure checks on the high and low pressure pumps, but not sure on the anti-siphon valve.


Checking to see if any of the marina mechanics that post on here have any advice/instructions that might help me? Is the valve right at the fuel line connection on the tank? The boat is an 04 298SC.



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Apparently no one else has had this problem, but I'll give an account of what happened to mine in the event they do.


My port engine would start and idle fine. When taking off to get on plane it would (after about 10 seconds) start losing RPM's and "popping". I would immediately pull the throttle back and it would go back to idling just fine, but I noticed the fuel pump was making a whining or "screaming" noise. I thought it could be a corroded rotor cap (causing the popping sound) which I pulled, inspected, cleaned and replaced. It didn't fix the issue so I ruled out ignition.


I then changed the fuel filter and it didn't fix it either. I then read online somewhere that the anti-siphon valves could get stuck and starve the engine of fuel at higher RPM's. It sounded to me like this was more than plausable and the starvation could make the pump produce the whining if it was laboring to get fuel from the tank. In the back of my mind, I knew it was probably the fuel pump, but hated the idea of dropping $750 for the fuel cell.


I checked the anti-siphon valve which is located (on the 298SC) under the plywood plate they install the macerator pump on. If you remove the (4) screws of that panel, you can get to all of the fuel lines/anti-siphon valves. Anyway, the valve was clean as it could be. Next stop - fuel pump.


I tested the high pressure pump and the pressure was right on target. The weird thing was the low pressure pump tested fine as well, but it just didn't sound right - not like the starboard side anyway. When I turned the key on, it just sounded like it struggled despite what the gauge was telling me. I ended up biting the bullett and buying a new fuel cell (consists of both the high and low pressure pumps). I put it on and it fixed the problem. My only guess is the old pump would heat up and start to fail.


I hope this helps anyone else who might experience the same problem.

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